From Lightroom Mobile (without going back to the desktop app), is it possible to share only specific photos within a collection while using the "web collection sharing" feature?

For example, could I share only 5 star rated photos? I want to be able to continue editing some photos from the same collection without sharing them. So simply removing them from the shared collection is not a solution.

One work-around solution would be duplicating the collection as a new collection, allowing me to remove photos from the shared collection without losing the ability to edit the unshared photos. However, I don't believe this can be done in Lightroom Mobile either.

You can move photos to another collection. You can even create a new collection to put them in. This way, you can separate the photos from one collection, and share the others, without returning to the desktop app.